Ion implantation is a process for introducing dopants, additives, or impurities into a substrate via bombardment. Known ion implantation systems or apparatus may comprise an ion source and a series of beam-line components. The ion source may comprise a chamber where desired ions are generated. The ion source may also comprise a power source and an extraction electrode assembly disposed near the chamber. The beam-line components, may include, for example, a mass analyzer, a first acceleration or deceleration stage, a collimator, and a second acceleration or deceleration stage. Much like a series of optical lenses for manipulating a light beam, the beam-line components can filter, focus, and manipulate ions or ion beam having desired species, shape, energy, and other qualities. The ion beam passes through the beam-line components and may be directed toward a substrate mounted on a platen or clamp. The substrate may be moved in one or more dimensions (e.g., translate, rotate, and tilt) by an apparatus, sometimes referred to as a roplat. Other ion implantation apparatus including compact ion implantation arrangements where a substrate may be located within a plasma chamber or in a process chamber adjacent to a plasma chamber.
In beamline ion implanters, the ion implanter system generates a stable, well-defined ion beam for a variety of different ion species and extraction voltages to desirably operate the ion source for extended periods of time, while avoiding the need for maintenance or repair. After several hours of normal operation using source gases (such as AsH3, PH3, BF3, and other species), beam constituents may eventually create deposits on beam optics. Beam optics within a line-of-sight of a wafer to be implanted may also become coated with residues from the wafer, including Si and photoresist compounds. These residues build up on the beam-line components, causing spikes in the DC potentials during normal operation (e.g., in the case of electrically biased components) and eventually flake off, causing an increased likelihood of particulate contamination on the wafer.
To mitigate possible flaking issues, components having buildup may be removed for cleaning periodically, requiring significant down time. Repurposing an ion beam line used for implantation to periodically etch beamline components to reduce flaking may in principle help avoid flaking. A drawback of this latter approach is the presence of shadowed surfaces of components not in the direct line of sight of the ion beam, including surfaces facing a wafer, may not be etched by the ion beam, allowing buildup and flaking to occur on the shadowed surfaces.